It will be argued that in the process of chemical adsorption/desorption on a surface, a molecule with several electrons involved in formation of chemical bonds will always pass extended regions of degeneracy with electronically excited molecular configurations. Such degeneracy allows a ”vibronic” coupling mechanism between the ground and the electronically-excited states; a process similar to Inverse Electronic Relaxation may start to play a significant role. Conditions at which the above-mentioned phenomenon can appear as a particularly strong nonadiabatic effect will be examined and links drawn to experimental observations made on several systems as well as to theoretical attempts to account for these effects.
Particularly, the observations reporting a strong dumping of internal vibrations in molecules will be discussed and reconsidered with an attempt to implement the new ideas. In the model proposed, dissipation of the energy from “hot” coordinate(s) of the system is resonantly-enhanced by excited electronic configuration; the mechanism may lead to dissipation of large energy quanta in form of excitons, rather than to direct generation of electron-hole pairs commonly discussed in the connection to non-adiabatic effects within the “friction force” and “hole diving” models . It will be argued that experiments with electronically excited species can provide vital information for understanding of the very nature of passways of surface chemical reactions and of the corresponding reaction dynamics effects.
|Period||31. Oct 2007|
|Event title||About vibronic origin of the strong non-adiabatic effects on passways of elementary (surface) chemical reactions: null|